Posted on by Nathan O'Brien

The problem of biofouling

By Jonathan Sierke

Water purification is an essential process to provide potable water and remove dangerous contaminants from wastewater to prevent their entry into the wider environment. One important method of water purification is by using water filtration membranes, which allow water to pass through but prevent the passage of contaminants too large to fit through the pores of the membrane. However, a significant problem with using water filtration membranes is biofouling, where bacteria create a biofilm on the membrane surface.[1, 2] This restricts the passage of water through the membrane, which reduces the efficiency of the filtration process, increasing energy and time required.

In my research, I incorporated an antibacterial compound, eugenyl methacrylate[3, 4] (a compound derived from eugenol, the major constituent of clove oil), into PVDF water filtration membranes using a UV cross-linking process, which binds the antibacterial compound into the membrane. The antibacterial performance of the membranes was then analysed by immersing the membranes in a nutrient solution for different lengths of time, to promote the growth of bacteria. The number of the bacterial cells on the membrane surface was then counted using Scanning Electron Microscopy (SEM). My results indicated that with the incorporation of 20 wt% of eugenyl methacrylate roughly halved the number of bacterial cells on the membrane surface after 6 days of immersion in the nutrient solution, with SEM images of the membrane surfaces (Figure 1) displaying the reduction of bacterial cell adhesion. These results indicate eugenyl methacrylate is a promising material to provide antibacterial and biofouling resistant membranes for water filtration.

Figure 1. SEM images of the surface of PVDF membranes incorporating 0 wt% (left) and 20 wt% (right) of eugenyl methacrylate, after immersion in a nutrient solution for 6 days. Note the large reduction in the number of bacterial cells (white rods) on the membrane surface when 20 wt% of eugenyl methacrylate has been incorporated.

References:

  1. Herzberg, M. and Elimelech, M., “Biofouling of reverse osmosis membranes: Role of biofilm-enhanced osmotic pressure.” Journal of Membrane Science, 2007. 295(1-2): p. 11-20.
  2. Herzberg, M., Kang, S., and Elimelech, M., “Role of Extracellular Polymeric Substances (EPS) in Biofouling of Reverse Osmosis Membranes.” Environmental Science & Technology, 2009. 43(12): p. 4393-4398.
  3. Rojo, L., Barcenilla, J.M., Vázquez, B., González, R., and San Román, J., “Intrinsically Antibacterial Materials Based on Polymeric Derivatives of Eugenol for Biomedical Applications.” Biomacromolecules, 2008. 9(9): p. 2530-2535.
  4. Rojo, L., Vazquez, B., Parra, J., López Bravo, A., Deb, S., and San Roman, J., “From Natural Products to Polymeric Derivatives of “Eugenol”:  A New Approach for Preparation of Dental Composites and Orthopedic Bone Cements.” Biomacromolecules, 2006. 7(10): p. 2751-2761.
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